I hereby award you the last word....as I am tired...

Zyxt or should you prefer Zyxst or Zyzzyva

Zyxt is listed as the last word in the online Oxford English Dictionary, an obsolete Kentish word that is the second singular indicative present form of the verb see. The next-to-last is zyxst, an obsolete word meaning 'sixth'. Several online dictionaries list the word zyzzyva, a tropical American weevil, as the last word in the letter Z.

source: http://dictionary.reference.com/help/faq/language/w41.html

CB